1. Field of the Invention
The present invention relates to a display method and apparatus in which a display unit composed of a plurality of display cells each having the capability of a memory is employed. More particularly, the present invention relates to a display method and plasma display panel (PDP) apparatus in which an AC type PDP capable of expressing multilevel gray-scale at high resolution is employed
2. Description of the Related Art
The present invention relates to a display apparatus for displaying data by producing light at cells after writing the data to be displayed at the locations of the cells, wherein one frame is divided into a plurality of subframes associated with different luminance levels, and subframes during which light is produced are combined in order to achieve gray-scale display. This approach has been employed in a wide range of flat-panel display apparatuses. A typical example is a PDP apparatus. A description will follow taking an AC type PDP apparatus as an example. However, the present invention is not limited to this type of display apparatus. For example, the present invention can also be adapted to a display apparatus in which a liquid-crystal display panel is used in combination with a light source whose on and off states are controllable in order to achieve a gray-scale display.
In an AC type PDP, each subframe is subdivided into a reset period, an addressing period, and a sustaining period. Gray-scale display is achieved by associating bits of display data with the subframes, and changing the lengths of the sustaining periods within the subframes according to weights imposed on the bits. In recent years, a PDP apparatus has been required, like other types of display apparatuses, to offer high resolution and high display quality. To ensure a high display quality, it is necessary to increase the number of display gray-scale levels and raise the frame frequency. Moreover, the number of scanning lines must be increased in order to improve resolution. In an AC type PDP apparatus, a subframe approach is adopted for controlling gray-scale. To increase the number of gray-scale levels, it is necessary to increase the number of subframes. Increases in resolution and in number of display gray-scale levels cause the frame frequency to decrease. To increase the number of scanning lines and the number of subframes without any decrease in frame frequency, it is necessary to shorten one subframe and reduce the time required for each addressing scan. However, when an addressing period is shortened, the margin of operation is reduced. It is therefore difficult to reduce time under the current situation.
As a method for solving the foregoing problem a method in which interlaced-scanning is adopted for an addressing scan, and the number of addressing scans (display lines) to be carried out during all subframes is halved, has been adopted in the past. However, when the known interlaced-scanning addressing scan is adopted, occurrence of flicker in a display picture becomes a problem. Occurrence of flicker becomes a significant problem especially when both lines and characters are displayed in the same manner as they are on a display screen of a computer. Flicker is alleviated by shortening a frame. For the aforesaid reasons, there is a difficulty in shortening the frame Tf.